Element abundance patterns in carbonate globules and rims from

McKay et al. [1] reported possible evidence for ancient biological activity in carbonate globules and the rims on the carbonate globules from the AH84001 meteorite. Both the formation temperature and the origin of these carbonate globules and rims is controversial. McKay et al. [1] suggest the carbonates formed at low temperatures, while Harvey and McSween [2] indicate they formed at significantly higher temperatures. While McKay et al. [1] suggest that these carbonates contain a number of indicators suggesting they may have been derived from ancient biological activity, Bradley et al. [3] propose that some of the features formed from vapors at high temperatures, possibly in the hot gases from volcanic vents. Since element abundance patterns have previously proven useful in constraining the formation temperatures and formation mechanisms of planetary materials and meteorites, we have begun a study of the element abundances in carbonate globules and rims from AH84001 using the X-Ray Microprobe (XRF Microprobe) on Beamline X26A of the National Synchrotron Light Source at Brookhaven National Laboratory. This instrument, which has previously been employed in the chemical analysis of interplanetary dust particles, has been described in Flynn and Sutton [4]. The carbonates described by McKay et al. [1] consist of transparent, orangish carbonate globules ~50 to 100 microns in size coated with opaque rims about 10 microns thick. Samples were prepared by extracting fragments of a carbonate globule and of rim material from fresh fracture surfaces of AH84001. A transparent orangis